The present invention relates generally to focal plane array technology and, more specifically, to a thermally isolated focal plane array and interconnect structure.
A focal plane array comprises an array of infrared detectors, a cooling arrangement or refrigerator for cooling the detectors, and a readout arrangement for reading out the charge on the detectors. In conventional infrared focal plane arrays, the readout is connected to each detector by means of indium bump interconnects. These indium bump interconnects have a low thermal resistance. This requires the readout to operate at the same temperature as the detector, in fact, the readout acts as a heat sink for the detector. Since the readout must be maintained at or below a typical operating temperature of 10-20 degrees Kelvin, the noise tends to increase substantially as the readout temperature is lowered below the freezeout temperature of silicon, and the heat generated in the readout places a significant load on the refrigerator. Thus the performance of conventional focal plane arrays has been limited by readout noise and power dissipation.
A thermally insulating and electrically conductive interconnect has been developed by the assignee of the present invention that addresses the interconnection of pyroelectric focal plane arrays. This interconnect and the process of making the interconnect is described in U.S. Pat. No. 4,740,700 issued to Shaham et al., which patent is incorporated herein by reference.
Accordingly, it is a feature of the present ivention to thermally optimize a focal plane array. Another feature of the present invention is to reduce the amount of power used by a focal plane array, and thereby to reduce it weight. A further feature of the invention is to provide an improved focal plane array having a lower refrigerator capacity. A still further feature of the present invention is the provision of a focal plane array having lessened readout noise.